1. Technical Field
The present invention relates generally to absorbent materials and processes for the manufacture thereof; and, more particularly, to absorbent materials which are readily degradable by incineration or the like following usage as an absorbent and which may be either hydrophilic or hydrophobic in nature, thereby permitting usage of the hydrophilic forms of the invention as industrial floor sweeps, beddings for use in animal transport, kitty litter and the like, while permitting usage of the hydrophobic forms of the invention for species specific absorption purposes such, merely by way of example, as the absorption of oil spills from both land and water environments, as well as absorption of other toxic liquid materials and/or other liquid contaminants.
More specifically, the present invention utilizes, as a basic ingredient, waste cellulose fibers of the type commonly generated in wood pulping or paper making operations; and, more particularly, waste cellulose fibers having a relatively low content of inorganic solids--e.g., clays and/or other silica compounds, commonly referred to as "fillers". Preferably, the waste cellulose fibers used with the present invention include not more than 10% inorganic solids by weight and, in any event, less than 30% inorganic solids by weight. Ideally, however, the waste cellulose fibers employed with the present invention have no inorganic solids content; but, as a practical matter, the waste streams from most pulp and/or paper mills will include some inorganic solids or "fillers". Typically, such waste cellulose fiber materials having relatively low inorganic solids content are generated as a waste bi-product at the discharge end of a sulfite bleach mill used in the pulping industry such, for example, as in the pulp mill of Georgia Pacific Corporation located in Bellingham, Wash. However, as the ensuing description proceeds, those skilled in the art will appreciate that the invention is not limited to use with the discharge wastes of sulfite bleach pulp mills but, rather, can be used with such materials generated in other conventional pulping and/or paper making processes that produce low inorganic solids content in the waste outflows.
2. Background Art
Heretofore clay-based materials and other inorganic absorbents have been utilized in the control and removal of undesired liquids from industrial floors and walkways and similar industrial environments. But, such materials are not: i) sufficiently effective as determined by absorptive capacity; ii) convenient as determined by bulk density, typically 25 to 40 lbs./ft..sup.3 ; or iii), readily decomposable or degradable, as the wholly inorganic constituents preclude incineration even when saturated with combustible liquid material or the like.
A recent advance in absorptive media entails the pelletization of cellulose fibers and clay and/or other inorganic solids as disclosed in U.S. Pat. No. 4,374,794--Kok. However, the action of pelletizing a combination of cellulose fibers and inorganic solids or "fillers" requires use of considerable force applied to the material in order to extrude it from a die orifice. The requisite force is a compressive action that: i) eliminates interstitial spaces in the body of the pellet; ii) creates a non-porous surface; iii) creates a dimensionally stable cylindrical shape; and iv), results in a product having a bulk density typically ranging from 25 to 40 lbs./ft..sup.3. Moreover, when used as an absorptive media on floor surfaces, the extruded pellets present a hazardous rolling interface between the floor surface and pedestrian traffic. Further, such extruded pellets exhibit low absorptive capacities.
Two other patents of interest are those recently issued to Papyrus Kopparfors A.B. of Molndal, Sweden as the assignee of Thomas Ericsson, U.S. Pat. No. 4,537,877, and as the assignee of Thomas Ericsson et al, U.S. Pat. No. 4,519,918. Thus, in the Ericsson '877 patent, the patentee discloses various examples of a particulate oil-absorbing composition comprising at least 50% by weight hydrophobic cellulose pulp fibers ". . . blended with at least 30% up to 50% of an inorganic cellulose paper pulp filler . . . ". See, Col. 1, lines 48 and 49 of U.S. Pat. No. 4,537,877. Unfortunately, the inclusion of large amounts of inorganic cellulose paper pulp fillers--including particularly amounts in the range proposed by the Ericsson comprising at least 30% by weight and ranging up to 50% by weight of the basic composition--presents a number of problems. First and foremost, the inorganic solids or "fillers" tend to increase the bulk density of the resulting product which generally ranges from 16 to 20 lbs./ft..sup.3 ; and, as a consequence, even though the product is hydrophobic, upon saturation with oil it will not float. Moreover, the large amount of inorganic solids present tends to reduce both the rate of absorption and the absorptive capacity of the product produced. Additionally, the inorganic solids are not readily flammable and/or degradable; and, cannot be satisfactorily disposed of by incineration, thus producing a significant quantity of non-degradable ash, which creates a high-cost disposal problem, and reducing the amount of heat that can be generated per cubic volume of waste material. The inorganic solids present further create significant dust problems resulting in eye and/or breathing irritants, undesirable abrasion of production equipment and, indeed, a severe explosion hazard.
In the Ericsson '877 patent, it is proposed to render the cellulose fibers hydrophobic by sizing with rosin; whereas in the Ericsson et al '918--a patent which is subject to all of the disadvantages mentioned above which are inherent in the Ericsson '877 patent--the fibers are rendered hydrophobic by impregnation with liquid resinous materials. In both cases, no provision is made for conditioning the particulate materials to insure that the fiber ends do not project outwardly from the fibrous particles: and, as a consequence, the particulate materials of Ericsson and Ericsson et al exhibit a fuzzy surface appearance which results in breakage of fiber ends, increasing the dust problem, while causing clinging and compaction of adjacent particles.